General Principles of Design, Drawing & Safety is a compact but high-yield section of ESE (IES) Paper I, common to all engineering disciplines. This module spans the engineering design process and factor of safety, BIS/ISO engineering drawing conventions, orthographic views and sectional representations, tolerances/fits/limits, and workplace safety legislation — with every formula, standard number, and numeric fact carried over, plus worked examples and diagrams for each topic.
After studying this chapter you will be able to:
This module has no strict subject prerequisite, but the drawing-conventions and tolerances/fits chapters connect closely with the manufacturing and machine-design portions of core engineering papers, while workplace safety links to Environmental Engineering and Project Management. Once you've worked through the chapters below, head to the Design, Drawing & Safety hub page to generate practice tests, or explore Study Material for other subjects.
Engineering design is a systematic, iterative process of converting needs/requirements into a product or system. Key stages: (1) Define problem; (2) Research and gather data; (3) Generate concepts; (4) Select best concept; (5) Detail design; (6) Prototype and test; (7) Iterate; (8) Manufacture and deliver.
| Principle | Description |
|---|---|
| Functionality | Design must fulfil its intended purpose reliably |
| Safety | Must not pose hazard to users, operators or environment; factor of safety applied |
| Ergonomics | Designed for human use — comfortable, efficient, minimises fatigue and errors |
| Aesthetics | Visually appealing and contextually appropriate |
| Economy | Minimum cost consistent with required performance and durability |
| Manufacturability | Design for ease of manufacture (DFM); minimise machining, use standard parts |
| Maintainability | Easy to inspect, service, repair; accessible components |
| Sustainability | Minimise environmental impact; use recyclable materials; energy-efficient operation |
Factor of safety definition and its governing factors are directly asked in ESE Paper I. Ergonomics and DFM (Design for Manufacture) principles are tested conceptually as well.
\(FOS = \dfrac{\text{Ultimate stress}}{\text{Working stress}} = \dfrac{\text{Failure load}}{\text{Design load}}\)
Steel structures: 1.5–2.5. Concrete: 3–4. Brittle materials: 4–6.
Define → Research → Generate concepts → Select → Detail design → Prototype/test → Iterate → Manufacture/deliver
Functionality, Safety, Ergonomics, Aesthetics, Economy, Manufacturability (DFM), Maintainability, Sustainability
Given: A steel component has an ultimate tensile stress of 400 MPa and is designed to operate at a working stress of 200 MPa. What is its factor of safety, and is this typical for steel structures?
Solution: \(FOS = \dfrac{400}{200} = 2.0\). This falls within the typical range of 1.5–2.5 used for steel structures.
Answer: FOS = 2.0 — a typical value for steel.
Given: A component is to be made from a brittle cast-iron material subject to uncertain, fluctuating loads. Should the designer choose a FOS closer to 1.5 or closer to 5?
Solution: Brittle materials fail suddenly without warning (no yielding), and load uncertainty further increases risk. Both factors call for a higher factor of safety — the typical brittle-material range is 4–6, so a FOS near 5 is appropriate rather than near 1.5 (which is more suited to well-characterised ductile steel under known loads).
Answer: Closer to 5, since brittle failure and load uncertainty both demand a higher FOS.
Given: A designer simplifies a bracket's shape to use fewer standard fasteners and reduce the number of machining operations. Which design principle does this best illustrate?
Solution: Reducing machining operations and using standard parts to ease production is the definition of Manufacturability (Design for Manufacture, DFM).
Answer: Manufacturability (DFM).
Fig. 1.1 — The eight stages of the engineering design process, from problem definition to manufacture and delivery.
| Standard | Content |
|---|---|
| IS 696 | Conventions for surface texture (roughness) |
| IS 9609 | Lettering on technical drawings (inclined and upright) |
| IS 11065 | General tolerances for linear dimensions |
| ISO 128 | General principles of presentation of drawings |
| ISO 2768 | General tolerances — untoleranced linear and angular dimensions |
| Sheet | Size (mm) |
|---|---|
| A0 | 841 × 1189 |
| A1 | 594 × 841 |
| A2 | 420 × 594 |
| A3 | 297 × 420 |
| A4 | 210 × 297 |
| Line Type | Appearance | Use |
|---|---|---|
| Continuous thick | Solid wide line | Visible edges and outlines |
| Continuous thin | Solid narrow line | Dimension lines, hatching, leader lines |
| Dashed thin | Short dashes | Hidden edges |
| Chain thin | Long dash–dot | Centre lines, axes of symmetry |
| Chain thin (thick at ends) | Long dash–dot–dot | Cutting planes for sections |
| Continuous thin zigzag | Freehand wavy | Break lines (short breaks) |
A0: 841×1189 mm · A1: 594×841 · A2: 420×594 · A3: 297×420 · A4: 210×297
Successive sizes are in the ratio \(\sqrt{2}:1\); each step halves the sheet area
Hidden edges = dashed thin line. Centre lines/axes of symmetry = chain thin (long dash–dot)
IS 696 (surface texture) · IS 9609 (lettering) · IS 11065 (general tolerances) · ISO 128 (presentation) · ISO 2768 (untoleranced dimensions)
Given: A0 sheet measures 841 mm × 1189 mm. If each successive sheet (A1, A2, ...) is obtained by halving the area of the previous one along its longer dimension, what is the approximate area of an A4 sheet relative to A0?
Solution: Each step from A0 to A4 involves 4 halvings (A0→A1→A2→A3→A4), so the area is reduced by a factor of \(2^4 = 16\). A0 area \(\approx 841 \times 1189 = 999{,}949\text{ mm}^2\); A4 area \(\approx \dfrac{999{,}949}{16} \approx 62{,}497\text{ mm}^2\), matching A4's actual 210×297 = 62,370 mm² (small rounding difference).
Answer: A4's area is approximately 1/16th of A0's area.
Given: A drafter needs to show an edge that is hidden behind another surface in the current view, and also mark the axis of symmetry of a cylindrical part. Which line types should be used for each?
Solution: The hidden edge should be drawn as a dashed thin line (short dashes). The axis of symmetry should be drawn as a chain thin line (long dash–dot pattern) — a centre line.
Answer: Hidden edge = dashed thin line; axis of symmetry = chain thin (centre) line.
Given: Which BIS standard governs the surface roughness conventions used on an engineering drawing?
Solution: IS 696 specifically covers conventions for surface texture (roughness) on engineering drawings, distinct from IS 9609 (lettering) or IS 11065 (general tolerances).
Answer: IS 696.
Fig. 2.1 — The six standard line types used in BIS/ISO engineering drawings.
First Angle Projection (European / BIS standard in India): Object placed in first quadrant; view projected onto planes behind the object. Front view (FV) → front plane; Top view → below FV; Side view → to the left of FV.
Third Angle Projection (American standard): Object placed in third quadrant; views appear in their natural position. Top view → above FV; Right side view → to the right of FV.
Symbol on drawing: First angle = circle with cone pointing left; Third angle = circle with cone pointing right.
| Type | Description |
|---|---|
| Full section | Cutting plane passes entirely through the object |
| Half section | Only half the object is cut; other half shows external features (for symmetric objects) |
| Offset section | Stepped cutting plane passes through multiple features |
| Revolved section | Cross-section of rib/spoke revolved 90° into the view |
| Removed section | Cross-section drawn outside the main view with reference |
Auxiliary view: used to show true shape of inclined surfaces; projected perpendicular to the inclined face.
Isometric drawing: 3D representation; all three axes at 120° to each other; measurements along axes are true length.
\(\dfrac{\cos 45^{\circ}}{\cos 30^{\circ}} = 0.816\) — isometric lengths ≈ 82% of true length
Top view goes BELOW front view (BIS/Indian standard); symbol = cone pointing left
Top view goes ABOVE front view (American standard); symbol = cone pointing right
Full · Half · Offset · Revolved · Removed sections
Given: A cube has a true edge length of 50 mm. What length should this edge be drawn as in an isometric drawing?
Solution: Isometric length = True length × Isometric scale = \(50 \times 0.816 = 40.8\text{ mm}\).
Answer: Approximately 40.8 mm.
Given: A symmetric cylindrical part needs to show internal bore features on one side while still displaying its external surface finish on the other side. Which sectional view type should be used?
Solution: A half section is specifically used for symmetric objects, cutting through only half the object to reveal internal features while the other half retains the external view.
Answer: Half section.
Given: On an Indian (BIS) engineering drawing, where should the top view of an object be placed relative to the front view?
Solution: India follows First Angle Projection (the European/BIS standard), in which the top view is placed below the front view — the opposite of the American Third Angle standard, where the top view is placed above the front view.
Answer: Below the front view (First Angle Projection).
Fig. 3.1 — First-angle projection (India/BIS, top view below) versus third-angle projection (USA, top view above).
| Term | Definition |
|---|---|
| Nominal size | Basic theoretical size specified on drawing |
| Basic size | Size from which deviations are applied (same as nominal for standard fits) |
| Tolerance | Permissible variation = \(\text{Upper limit} - \text{Lower limit}\) |
| Allowance | Intentional (designed) difference between mating parts; minimum clearance or maximum interference |
| Upper Deviation (ES/es) | \(\text{Upper limit} - \text{Basic size}\) (ES for hole; es for shaft) |
| Lower Deviation (EI/ei) | \(\text{Lower limit} - \text{Basic size}\) (EI for hole; ei for shaft) |
| Fit Type | Condition | Application |
|---|---|---|
| Clearance fit | Shaft always smaller than hole; positive clearance | Rotating/sliding parts — bearings, pistons |
| Interference fit | Shaft always larger than hole; assembly requires force/heating | Press-fitted hubs, gears, couplings |
| Transition fit | May be clearance or interference depending on actual sizes | Keys, locating fits |
Hole-basis system (preferred in India): hole tolerance fixed (H); shaft varies. H7/f6 = clearance fit; H7/k6 = transition fit; H7/p6 = interference fit.
Shaft-basis system: shaft tolerance fixed (h); hole varies. Used when shaft from stock (e.g. standard bar stock) is the common element.
\(\text{Tolerance} = \text{Upper limit} - \text{Lower limit}\)
Upper: ES/es = Upper limit − Basic size. Lower: EI/ei = Lower limit − Basic size.
Clearance (shaft < hole) · Interference (shaft > hole) · Transition (either)
H7/f6 = clearance · H7/k6 = transition · H7/p6 = interference
Given: A shaft has an upper limit of 25.05 mm and a lower limit of 24.98 mm. What is its tolerance?
Solution: Tolerance = Upper limit − Lower limit = \(25.05 - 24.98 = 0.07\text{ mm}\).
Answer: 0.07 mm.
Given: A hole has limits of 25.00–25.02 mm and a mating shaft has limits of 24.98–24.99 mm. Is this a clearance, interference, or transition fit?
Solution: The shaft's maximum size (24.99 mm) is smaller than the hole's minimum size (25.00 mm) in every possible combination, so the shaft is always smaller than the hole — this is a clearance fit.
Answer: Clearance fit (shaft is always smaller than the hole).
Given: Why does India's BIS standard prefer the hole-basis system over the shaft-basis system for general manufacturing?
Solution: In the hole-basis system, the hole's tolerance is fixed (designated H) while the shaft size is varied to achieve the desired fit. This is preferred because holes are typically machined with standard-sized tools (drills, reamers), making it more practical to keep hole tolerance fixed and vary the (more easily adjustable) shaft size.
Answer: Because standard tooling (drills, reamers) produces fixed hole sizes more practically than variable ones, so the hole-basis system reduces the number of tools needed.
Fig. 4.1 — Clearance, transition, and interference fits, showing the relative shaft-to-hole size relationship for each.
| Act / Rule | Scope |
|---|---|
| Factories Act, 1948 | Health, safety, welfare of workers in factories; working hours; occupational hazards |
| Mines Act, 1952 | Safety in mines and quarries |
| Building & Other Construction Workers Act, 1996 | Safety of construction workers; health and welfare provisions |
| Occupational Safety, Health and Working Conditions Code, 2020 | Consolidated code replacing multiple older acts |
| IS 4082 | BIS standard for stacking and storage of materials on construction sites |
\(Risk = Probability \times Severity\) (consequence). Risk matrix: Low / Medium / High / Critical — drives control priority.
Hierarchy of controls (preferred order):
| Hazard | Controls |
|---|---|
| Working at height (falls) | Scaffolding with guard rails; harnesses; safety nets; edge protection |
| Falling objects | Toe boards; debris nets; helmets; exclusion zones |
| Electrical hazards | Lockout-tagout (LOTO); insulation; residual current devices (RCD) |
| Excavation collapse | Shoring; battering; inspection before each shift |
| Crane and lifting operations | SWL markings; banksman; pre-lift checks; exclusion zones |
| Noise | Engineering controls; hearing protection (85 dB exposure limit per IS) |
\(Risk = Probability \times Severity\)
Elimination → Substitution → Engineering controls → Administrative controls → PPE
85 dB(A) for 8-hour exposure (per Indian standards)
Factories Act 1948 · Mines Act 1952 · BOCW Act 1996 · OSH Code 2020 · IS 4082 (material stacking)
Given: A construction site has identified a hazard from workers manually mixing a toxic chemical. Rank two possible interventions — installing local exhaust ventilation, versus issuing respirator masks — according to the hierarchy of controls.
Solution: Local exhaust ventilation is an engineering control (level 3), which is preferred over respirator masks, which are PPE (level 5, the last resort). Per the hierarchy of controls, engineering controls should be implemented before relying on PPE.
Answer: Local exhaust ventilation (engineering control) should be prioritised over respirator masks (PPE).
Given: Which Indian act specifically governs the health, safety, and welfare of workers employed in factories, including working hours?
Solution: The Factories Act, 1948 specifically governs health, safety, and welfare provisions, along with working hours and occupational hazards, for workers in factories.
Answer: The Factories Act, 1948.
Given: Workers face a risk of falling objects on a multi-storey construction site. Name two specific controls used to manage this hazard.
Solution: Toe boards (preventing objects from rolling off edges) and debris nets (catching falling material), along with helmets and exclusion zones, are standard controls for the falling-objects hazard.
Answer: Toe boards and debris nets (also helmets and exclusion zones).
Fig. 5.1 — The hierarchy of hazard controls: Elimination (most effective) down to PPE (last resort).
\(\dfrac{\text{Ultimate stress}}{\text{Working stress}}\)
210 × 297 mm
BIS / Indian standard; top view below front view
Dashed (short dash) lines
Shaft always smaller than hole
Shaft always larger than hole
H designation for hole; shaft designation varies
IT01 finest → IT18 coarsest
Elimination → Substitution → Engineering → Admin → PPE
85 dB(A) for 8-hour exposure
\(Risk = Probability \times Severity\)
\(\cos 45^{\circ}/\cos 30^{\circ} = 0.816\) — ~82% of true length
| Topic | Prelims/Paper I Focus |
|---|---|
| Principles of Design | FOS definition and typical ranges; design principle matching (functionality, DFM, ergonomics, etc.) |
| Drawing Conventions | IS/ISO code numbers; A-series sheet sizes; line type identification |
| Views and Sections | First vs third angle projection; sectional view type matching; isometric scale calculation |
| Tolerances, Fits & Limits | Tolerance/deviation numericals; clearance vs interference identification; hole-basis system |
| Workplace Safety | Hierarchy of controls sequencing; legislation-scope matching; noise limit facts |
Q1. A component has an ultimate stress of 350 MPa and is designed with an FOS of 2.5. What is its working stress?
Q2. A0 sheet area is 841 × 1189 mm. How many A4 sheets (each 210 × 297 mm) fit within the area of one A0 sheet?
Q3. A true length of 100 mm is drawn in isometric projection. What length (to the nearest mm) should be drawn?
Q4. A shaft's upper limit is 30.02 mm and lower limit is 29.97 mm. What is the tolerance?
Q5. Given the hierarchy of controls has 5 levels (Elimination, Substitution, Engineering, Administrative, PPE), if a hazard is controlled using training and work permits only, which level is this, counting from the top?